The present invention relates generally to rolling mills. More particularly, the invention concerns rolling mills for piercing solid billet as well as for elongating the pierced shell in the manufacture of seamless pipe and tube.
Piercing of solid billet for the production of seamless tubes is well-known in the art, dating back over the past 100 years. For example, U.S. Pat. No. 618,917 to Stiefel discloses a piercing mill having two conically shaped rolls oriented in a horizontal position and U.S. Pat. No. 2,025,148 to Bannister discloses a piercing mill having two conically shaped rolls oriented in a vertical position, that is, one work roll positioned above the other.
Heretofore, when different diameter product is to be rolled in a conventional piercer or elongator, a substantial amount of mill downtime is required in order to make the necessary changes in the roll spacing, roll feed angles and/or to change the rolls themselves. Substantial time is also required for changing of guide shoes in conventional piercer mills. It is also commonplace in the prior art to dedicate a particular mill as a piercing mill and a second mill as an elongator mill.
The problems of prior art piercing mills involving excessive downtime for roll gorge adjustment and/or for feed angle adjustment are solved by the present invention. In addition, the present invention provides a vertical piercing mill or elongator mill in which roll changes can be made with a minimum of lost production time and manpower. The invention also provides means for quickly changing worn stationary guide shoes or guide discs.
Still further, the present invention provides a cone type piercer or elongator mill of compact and economical design in which the conventional mill cap and associated equipment are eliminated. Thus, the present invention reduces downtime significantly over prior art piercing/elongator mills so as to maximize production efficiency while concurrently reducing capital expense for the mill itself and its installation.